Passive optical switching will be achieved, if photoinduced electron-transfer is associated with a new absorption band of a radical pair to cut off a light beam. Active switching should be observed, when the electrontransfer process is accompanied by light emission.(1) Transient absorption due to photogenerated radical pairs was investigated by the use of viologen as the electron acceptor (A). Either porphyrin or phenothiazine unit was the electron donor (D). The radical pair was easily generated, when the D and A were held each other within 1.5 nm. The lifetime of the radical pair was a few microseconds, but it could be easily extended up to 10 microseconds in the presence of external magnetic fields above 0.3 T. Photogeneration of the radical pairs was facilitated by molecular complexation. Transient absorption due to the radical pair could be used to construct passive switching elements.(2) Optical Second-Harmonic Generation (SHG) was observed by the use of amphiphloic ruthenium complexes incorporated into LB films. Metal to ligand charge-transferred state (MLCT) was responsible to the SHG. The intensity of the SHG at 532 nm could be remarkably reduced on laser excitation of the ML CT transition. This is the first observation of optical modulation of SHG intensity. Active switching should be achieved by virtue of this phenomenon.